JP2018193479A - Ionic conductive material - Google Patents

Abstract

To provide a novel ionic conductive material.SOLUTION: There is provided an ionic conductive material containing a -CO-O-PO structure-containing polymer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ion conductive material.

  Secondary batteries typified by lithium ion secondary batteries are currently used mainly as power sources for portable electronic devices, and are also put into practical use as power sources for electric vehicles. Along with the diversification of usage modes, there is a demand for higher capacity of secondary batteries. Therefore, studies have been made to increase the capacity of secondary batteries by driving them at a high voltage. However, when the secondary battery is driven at a high voltage, there is a problem that oxidative decomposition of the electrolytic solution due to contact with the positive electrode active material in an oxidized state occurs.

  Therefore, as a technique for reducing direct contact between the positive electrode active material and the electrolytic solution, a technique for forming a protective layer on the surface of the positive electrode active material layer containing the positive electrode active material has been proposed.

  For example, Patent Document 1 discloses a technique for providing a coat layer that covers the surface of a positive electrode active material. Specifically, a technique is disclosed in which a positive electrode composed of a current collector and a positive electrode active material layer is immersed in a polyethyleneimine solution and a polyethylene glycol solution, and the positive electrode is coated with a polymer.

  Patent Document 2 also discloses a technique of providing a coat layer that covers the surface of the positive electrode active material. Specifically, a technique is disclosed in which a positive electrode composed of a current collector and a positive electrode active material layer is immersed in a polyethylene glycol solution, and the positive electrode is coated with a polymer.

JP 2013-243105 A JP 2014-096343 A

  However, since the polymer is inherently a resistance factor against the movement of charge carriers such as lithium ions, it can be said that the secondary battery to which the technology disclosed in Patent Document 1 and Patent Document 2 is applied has a problem in the function as a battery. .

  This invention is made | formed in view of this situation, and it aims at providing the new ion conductive material which is excellent in ion conductivity although it is a polymer.

  Now, it is considered that a polymer having excellent ion conductivity needs a moving space surrounded by polar groups for smoothly moving charged ions. Therefore, the present inventor has conceived of using a carboxylic acid group-containing polymer. However, although the material manufactured using polyacrylic acid as a carboxylic acid group containing polymer was ion-conductive, its degree was low and was not satisfactory.

  As a result of further studies by the present inventor, the present inventor has found that a membrane produced using a reaction product of a carboxylic acid group-containing polymer and a phosphor oxide exhibits a satisfactory level of ionic conductivity. Based on this discovery, the present inventor has completed the present invention.

  The ion conductive material of the present invention is characterized by containing a -CO-O-PO structure-containing polymer. Moreover, the manufacturing method of the ion conductive material of this invention includes the reaction process of a carboxylic acid group containing polymer or its salt, and a pentavalent phosphorus compound.

  According to the present invention, a new ion conductive material can be provided.

2 is an infrared absorption spectrum of Example 1. 2 is an infrared absorption spectrum of Example 2. 2 is an infrared absorption spectrum of Comparative Example 1.

  Below, the form for implementing this invention is demonstrated. Unless otherwise specified, the numerical range “ab” described herein includes the lower limit “a” and the upper limit “b”. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from these numerical ranges can be used as new upper and lower numerical values.

  The ion conductive material of the present invention is characterized by containing a -CO-O-PO structure-containing polymer. The manufacturing method of the ion conductive material of this invention includes the reaction process of a carboxylic acid group containing polymer or its salt, and a pentavalent phosphorus compound.

The —CO—O—PO structure in the —CO—O—PO structure-containing polymer is formed by a reaction step between a carboxylic acid group-containing polymer or a salt thereof and a pentavalent phosphorus compound. For example, if the reaction of polyacrylic acid, which is a carboxylic acid group-containing polymer, and diphosphorus pentoxide, which is a pentavalent phosphorus compound, the reaction is considered to proceed, for example, according to the following reaction formula. In addition, the following reaction formula expresses only a part of the assumed reaction, and many reactions other than this reaction formula are assumed. It is also assumed that other carboxylic acid groups react with the product generated by this reaction formula.
2 (—CO—OH) + P ₂ O ₅ → (—CO—O—PO (OH)) ₂ O

Further, if the above reaction proceeds in the presence of water, it is considered that the reaction proceeds, for example, as shown in the following reaction formula.
2 (-CO-OH) + P 2 O 5 + H 2 O → 2 (-CO-O-PO (OH) 2)
Further, if the above reaction proceeds in, for example, an ethanol solvent, the reaction is considered to proceed as shown in the following reaction formula, for example.
2 (-CO-OH) + P 2 O 5 + 4EtOH → 2 (-CO-O-PO (OEt) 2) + 3H 2 O

  Compared to the —CO—OH group present in the carboxylic acid group-containing polymer, the —CO—O—PO structure is considered to have a low interaction with charge carriers such as lithium ions although it is a polar group. Therefore, it can be said that the ion conductive material of the present invention is excellent in ion conductivity.

  In the method for producing an ion conductive material of the present invention, the carboxylic acid group-containing polymer or a salt thereof is not particularly limited as long as it is a polymer containing —COOH or a salt thereof in the molecule. Examples of the salt include metal salts such as Li, Na, K, Mg, and Ca, ammonium salts, and amine salts.

  Specific examples of the carboxylic acid group-containing polymer include polyacrylic acid, polymethacrylic acid, and carboxymethylcellulose. In addition, as a carboxylic acid group-containing polymer, a homopolymer obtained by homopolymerizing a carboxylic acid group-containing monomer, a copolymer obtained by copolymerizing a plurality of types of carboxylic acid group-containing monomers, and a carboxylic acid group-containing monomer and other monomers are copolymerized. Other copolymers may be employed. Carboxylic acid group-containing monomers include acrylic acid, methacrylic acid, vinyl benzoic acid, crotonic acid, pentenoic acid, angelic acid, tiglic acid, itaconic acid, mesaconic acid, fumaric acid, maleic acid, methylmaleic acid, glutaconic acid, 2 -Allylmalonic acid, 4-methyl-3-pentenoic acid, 2- (1-methylethylidene) succinic acid, 2,4-hexadienedioic acid, and acetylenedicarboxylic acid can be exemplified.

  Examples of the weight average molecular weight of the carboxylic acid group-containing polymer or a salt thereof include 5,000 to 2,000,000, 10,000 to 1800000, 25,000 to 1500,000, and 50,000 to 1,000,000.

Examples of the pentavalent phosphorus compound include pentavalent phosphorus oxide, pentavalent phosphorus halide, and pentavalent halogenated phosphoryl. Specifically, P ₂ O ₅ , PF ₅ , PCl ₅ , and PBr ₅ can be exemplified. , POF ₃ , POCl ₃ , POBr ₃ can be exemplified. From the viewpoint of safety, P ₂ O ₅ is preferable as the pentavalent phosphorus compound.

  The -CO-O-PO structure-containing polymer is preferably a polymer containing a large number of -CO-O-PO structure-containing monomer units from the viewpoint of ion conductivity. The —CO—O—PO structure-containing monomer unit is preferably present in an amount of 40 to 100 mol%, and preferably present in an amount of 60 to 100 mol% with respect to all the monomer units constituting the —CO—O—PO structure-containing polymer. More preferably, it is present at 80 to 100 mol%, more preferably 90 to 100 mol%. All of the monomer units constituting the —CO—O—PO structure-containing polymer may be —CO—O—PO structure-containing monomer units. In order to produce a suitable —CO—O—PO structure-containing polymer, it is possible to react as many carboxylic acid groups as possible among the carboxylic acid groups present in the starting carboxylic acid group-containing polymer with a pentavalent phosphorus compound. That's fine.

  The ratio of the —CO—O—PO structure to the unreacted carboxylic acid group in the —CO—O—PO structure-containing polymer is preferably within the range of 10: 5 to 10: 0, and is preferably 10: 3 to 10: 0. Within the range, more preferably within the range of 10: 1 to 10: 0, still more preferably 10: 0.

  The reaction between a carboxylic acid group and a pentavalent phosphorus compound is not limited to a reaction between one carboxylic acid group and one pentavalent phosphorus compound, but a reaction between two carboxylic acid groups and one pentavalent phosphorus compound. A reaction between three carboxylic acid groups and one pentavalent phosphorus compound is also envisaged.

  In addition, in the -CO-O-PO structure-containing polymer, a polymer having a crosslinked structure in which phosphorus is crosslinked, which is formed by reacting two molecules of a raw material carboxylic acid group-containing polymer with a pentavalent phosphorus compound, is also assumed. .

  Examples of the weight average molecular weight of the —CO—O—PO structure-containing polymer include ranges of 5000 to 4000000, 10000 to 3600000, 25000 to 3000000, and 50000 to 2000000.

  In the reaction step of the method for producing an ion conductive material of the present invention, the value of (number of moles of carboxylic acid groups in the carboxylic acid group-containing polymer to be used) / (number of moles of phosphorus in the pentavalent phosphorus compound to be used) is Within the range of 0.1 to 2, more preferably within the range of 0.2 to 1.5, even more preferably within the range of 0.3 to 1, and particularly preferably within the range of 0.4 to 0.8. preferable.

  In the reaction step, it is preferable to coexist a solvent from the viewpoint of suitably proceeding the reaction. As the solvent, those capable of dissolving the carboxylic acid group-containing polymer or a salt thereof are preferable. Examples of the solvent include alcohols such as methanol, ethanol, and propanol, acetone, N-methyl-2-pyrrolidone, and water.

  What is necessary is just to set reaction time and reaction temperature in a reaction process suitably. Furthermore, it is preferable to provide a heating step in which the reaction solution obtained in the reaction step is dried by heating to remove the solvent used and by-product water. The heating temperature may be appropriately set within a range in which the ion conductive material does not decompose, and a temperature equal to or higher than the boiling point of the solvent used is preferable. What is necessary is just to set a heating time suitably according to heating temperature.

Moreover, you may add a group 2 element compound to the reaction liquid obtained at the reaction process. By adding the Group 2 element compound, it is expected that a crosslinked structure of the Group 2 element compound is formed in the -CO-O-PO structure-containing polymer. When, for example, CaCO ₃ or Ca (OH) ₂ is used as the Group 2 element compound, the reaction is considered to proceed according to the following reaction formula.
2 (COO-PO (OH) 2) + CaCO 3 → -COO-PO (OH) -O-Ca-O-PO (OH) -OCO- + H 2 CO 3
2 (-COO-PO (OEt) ₂ ) + Ca (OH) _2- >-COO-PO (OEt) -O-Ca-O-PO (OEt) -OCO- + 2EtOH

  Examples of the Group 2 element of the Group 2 element compound include Be, Mg, Ca, Sr, Ba, and Ra. Examples of Group 2 element compounds include hydroxides, oxides, halides, carbonates, sulfates, and nitrates. The amount of the Group 2 element compound added is preferably an amount corresponding to half or less of the number of —CO—O—PO structures in the —CO—O—PO structure-containing polymer.

From the disclosure so far, as one embodiment of the ion conductive material of the present invention, an ion conductive material containing a —CO—O—PO (OR) ₂ structure-containing polymer (wherein R is independently hydrogen, an alkyl group, or Selected from Group 2 elements). The alkyl group here is derived from alcohols used in the reaction step.

  The ion conductive material of the present invention may contain an unreacted carboxylic acid group-containing polymer, and the ion conductive material of the present invention is publicly known within the scope of the present invention. Additives such as polymers can be blended. The ion conductive material of the present invention preferably contains a -CO-O-PO structure-containing polymer at 50% by mass or more, more preferably contains a -CO-O-PO structure-containing polymer at 70% by mass or more, More preferably, it is 90% by mass or more and contains a -CO-O-PO structure-containing polymer. Examples of the ion conductive material of the present invention include those composed only of a -CO-O-PO structure-containing polymer.

  The ion conductive material of the present invention can be used for various applications by taking advantage of its characteristics. For example, in a power storage device such as a secondary battery, a use as a protective layer covering the positive electrode, the negative electrode, or the separator, or the separator itself or a solid electrolyte is assumed. Moreover, you may mix | blend the ion conductive material of this invention with the positive electrode active material layer containing the positive electrode active material in a secondary battery, or the negative electrode active material layer containing a negative electrode active material. By blending the ion conductive material of the present invention in the active material layer, the ion conductive material of the present invention is disposed on the surface of the active material, thereby reducing direct contact between the active material and the electrolytic solution. Can do.

  Hereinafter, a power storage device including the ion conductive material of the present invention and an electrode coated with the ion conductive material of the present invention (hereinafter also referred to as the electrode of the present invention) will be described.

Examples of the power storage device include a primary battery, a secondary battery, and a capacitor. Hereinafter, the power storage device including the ion conductive material of the present invention is referred to as the power storage device of the present invention, the secondary battery including the ion conductive material of the present invention is referred to as the secondary battery of the present invention, and the ion conductivity of the present invention. The lithium ion secondary battery provided with the material may be referred to as the lithium ion secondary battery of the present invention.
Hereinafter, the electrode of the present invention and the power storage device of the present invention including the electrode of the present invention will be described through the description of a lithium ion secondary battery which is a typical example of the power storage device.

  The electrode of the present invention may be a positive electrode or a negative electrode. Specific embodiments of the electrode of the present invention include a current collector, an active material layer formed on the surface of the current collector, and a layer containing the ion conductive material of the present invention formed on the surface of the active material layer (Hereinafter, simply referred to as “ion conductive material layer”).

  A current collector refers to a chemically inert electronic conductor that keeps current flowing through an electrode during discharge or charging of a secondary battery such as a lithium ion secondary battery. The material of the current collector is not particularly limited as long as it is a metal that can withstand a voltage suitable for the active material to be used. The current collector material is at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel Examples of such a metal material can be given. The current collector may be covered with a known protective layer. What collected the surface of the electrical power collector by the well-known method may be used as an electrical power collector.

  When the potential of the positive electrode is 4 V or more on the basis of lithium, it is preferable to employ aluminum as the positive electrode current collector.

  Specifically, it is preferable to use a positive electrode current collector made of aluminum or an aluminum alloy. Here, aluminum refers to pure aluminum, and aluminum having a purity of 99.0% or more is referred to as pure aluminum. An alloy obtained by adding various elements to pure aluminum is referred to as an aluminum alloy. Examples of the aluminum alloy include Al—Cu, Al—Mn, Al—Fe, Al—Si, Al—Mg, Al—Mg—Si, and Al—Zn—Mg.

  Specific examples of aluminum or aluminum alloy include A1000 series alloys (pure aluminum series) such as JIS A1085 and A1N30, A3000 series alloys (Al-Mn series) such as JIS A3003 and A3004, JIS A8079, A8021, etc. A8000-based alloy (Al-Fe-based).

  The current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. Therefore, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 1 μm to 100 μm.

  The active material layer includes an active material that can occlude and release charge carriers such as lithium ions, and a binder and a conductive aid as necessary. The active material layer preferably contains the active material in an amount of 60 to 99% by mass, more preferably 70 to 95% by mass with respect to the mass of the entire active material layer.

As the positive electrode active material, the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Fe, Ge, Zn, Ru, At least one element selected from Sc, Sn, In, Y, Bi, S, Si, Na, K, P, and V, a lithium mixed metal oxide represented by 1.7 ≦ f ≦ 3), Li ₂ MnO ₃ can be mentioned. Further, as a positive electrode active material, a spinel structure metal oxide such as LiMn ₂ O ₄ , a solid solution composed of a mixture of a spinel structure metal oxide and a layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (wherein M is selected from at least one of Co, Ni, Mn, and Fe). Furthermore, as the positive electrode active material, tavorite compound (the M a transition metal) LiMPO ₄ F, such as LiFePO ₄ F represented by, Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate-based compound represented by be able to. Any metal oxide used as the positive electrode active material may have the above composition formula as a basic composition, and a metal element contained in the basic composition may be substituted with another metal element. Moreover, you may use as a positive electrode active material the thing which does not contain a charge carrier (for example, lithium ion which contributes to charging / discharging). For example, sulfur alone, compounds in which sulfur and carbon are compounded, metal sulfides such as TiS ₂ , oxides such as V ₂ O ₅ and MnO ₂ , compounds containing polyaniline and anthraquinone, and aromatics in their chemical structures, conjugated two Conjugated materials such as acetic acid organic materials and other known materials can also be used. Further, a compound having a stable radical such as nitroxide, nitronyl nitroxide, galvinoxyl, phenoxyl, etc. may be adopted as the positive electrode active material. When using a positive electrode active material that does not contain a charge carrier such as lithium, it is necessary to add a charge carrier to the positive electrode and / or the negative electrode in advance by a known method. The charge carrier may be added in an ionic state or in a non-ionic state such as a metal. For example, when the charge carrier is lithium, it may be integrated by attaching a lithium foil to the positive electrode and / or the negative electrode.

From the viewpoint of excellent and high capacity, and durability, as the positive electrode active material, the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, At least one element selected from Rh, Fe, Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V, 1.7 ≦ f ≦ 3) It is preferable to employ a lithium composite metal oxide.

  In the above general formula, the values of b, c, and d are not particularly limited as long as the above conditions are satisfied, but those in which 0 <b <1, 0 <c <1, 0 <d <1 are satisfied. And at least one of b, c, and d is in the range of 10/100 <b <90/100, 10/100 <c <90/100, 5/100 <d <70/100. More preferably, the ranges are 20/100 <b <80/100, 12/100 <c <70/100, 10/100 <d <60/100, 30/100 <b <70/100, More preferably, the ranges are 15/100 <c <50/100 and 12/100 <d <50/100.

  About a, e, and f, what is necessary is just a numerical value within the range prescribed | regulated by the said general formula, Preferably 0.5 <= a <= 1.5, 0 <= e <0.2, 1.8 <= f <= 2 0.5, more preferably 0.8 ≦ a ≦ 1.3, 0 ≦ e <0.1, 1.9 ≦ f ≦ 2.1, respectively.

From the viewpoint of excellent and high capacity, and durability, as a positive electrode active material, the _{Li x Mn 2-y A y} O 4 (A spinel structure, Ca, Mg, S, Si , Na, K, Al, P, Ga And at least one element selected from Ge and at least one metal element selected from transition metal elements such as Ni. 0 <x ≦ 2.2, 0 ≦ y ≦ 1). Examples of the value range of x include 0.5 ≦ x ≦ 1.8, 0.7 ≦ x ≦ 1.5, and 0.9 ≦ x ≦ 1.2. The value range of y is 0 ≦ y ≦ 0.8, 0 ≦ y ≦ 0.6 can be exemplified. Specific examples of the spinel structure compound include LiMn ₂ O ₄ and LiMn _1.5 Ni _0.5 O ₄ .

Specific examples of the positive electrode active material include LiFePO ₄ , Li ₂ FeSiO ₄ , LiCoPO ₄ , Li ₂ CoPO ₄ , Li ₂ MnPO ₄ , Li ₂ MnSiO ₄ , and Li ₂ CoPO ₄ F. As another specific positive electrode active material, Li ₂ MnO ₃ —LiCoO ₂ can be exemplified.

As the negative electrode active material, a material that can occlude and release charge carriers can be used. Therefore, there is no particular limitation as long as it is a simple substance, alloy, or compound that can occlude and release charge carriers such as lithium ions. For example, as a negative electrode active material, Li, group 14 elements such as carbon, silicon, germanium and tin, group 13 elements such as aluminum and indium, group 12 elements such as zinc and cadmium, group 15 elements such as antimony and bismuth, magnesium , Alkaline earth metals such as calcium, and group 11 elements such as silver and gold may be employed alone. Specific examples of the alloy or compound include tin-based materials such as Ag-Sn alloy, Cu-Sn alloy, Co-Sn alloy, carbon-based materials such as various graphites, SiO _x (disproportionated to silicon simple substance and silicon dioxide). Examples thereof include silicon-based materials such as 0.3 ≦ x ≦ 1.6), silicon alone, or composites obtained by combining silicon-based materials and carbon-based materials. In addition, as the negative electrode active material, oxides such as Nb ₂ O ₅ , TiO ₂ , Li ₄ Ti ₅ O ₁₂ , WO ₂ , MoO ₂ , Fe ₂ O ₃ , or Li _3-x M _x N (M = A nitride represented by (Co, Ni, Cu) may be employed. One or more of these materials can be used as the negative electrode active material.

  In view of the possibility of increasing the capacity, preferable negative electrode active materials include graphite, Si-containing materials, and Sn-containing materials.

Specific examples of the Si-containing material include Si alone and SiO _x (0.3 ≦ x ≦ 1.6) disproportionated into two phases of a Si phase and a silicon oxide phase. The Si phase in SiO _x can occlude and release lithium ions, and changes in volume as the secondary battery is charged and discharged. The silicon oxide phase has less volume change associated with charge / discharge than the Si phase. That is, SiO _x as the negative electrode active material realizes a high capacity by the Si phase and suppresses the volume change of the entire negative electrode active material by having the silicon oxide phase. If x is less than the lower limit value, the Si ratio becomes excessive, so that the volume change during charging and discharging becomes too large, and the cycle characteristics of the secondary battery deteriorate. On the other hand, when x exceeds the upper limit value, the Si ratio becomes too small and the energy density decreases. The range of x is more preferably 0.5 ≦ x ≦ 1.5, and further preferably 0.7 ≦ x ≦ 1.2.

In the SiO _x as described above, it is believed to alloying reaction with the silicon lithium and Si phase during charging and discharging of the lithium ion secondary battery may occur. And it is thought that this alloying reaction contributes to charging / discharging of a lithium ion secondary battery. Similarly, it is considered that the Sn-containing material described later can be charged and discharged by an alloying reaction between tin and lithium.

Specific examples of the Sn-containing material include Sn alone, tin alloys such as Cu—Sn and Co—Sn, amorphous tin oxide, and tin silicon oxide. SnB _0.4 P _0.6 O _3.1 can be exemplified as the amorphous tin oxide, and SnSiO ₃ can be exemplified as the tin silicon oxide.

  The Si-containing material and the Sn-containing material are preferably combined with a carbon material to form a negative electrode active material. Due to the composite, the structure of silicon and / or tin is particularly stabilized, and the durability of the negative electrode is improved. The above compounding may be performed by a known method. As the carbon material used for the composite, graphite, hard carbon, soft carbon or the like may be employed. The graphite may be natural graphite or artificial graphite.

  Specific examples of the Si-containing material include a silicon material disclosed in International Publication No. 2014/080608 (hereinafter simply referred to as “silicon material”).

The silicon material has a structure in which a plurality of plate-like silicon bodies are laminated in the thickness direction. For example, the silicon material is subjected to a process of synthesizing a layered silicon compound containing polysilane as a main component by reacting CaSi ₂ with an acid, and further a process of heating the layered silicon compound at 300 ° C. or higher to desorb hydrogen. It is manufactured.

The production method of the silicon material is represented by the following ideal reaction formula when hydrogen chloride is used as the acid.
3CaSi ₂ + 6HCl → Si ₆ H ₆ + 3CaCl ₂
Si ₆ H ₆ → 6Si + 3H ₂ ↑

However, in the upper reaction for synthesizing Si ₆ H ₆ which is polysilane, water is usually used as a reaction solvent from the viewpoint of removing by-products and impurities. Since Si ₆ H ₆ can react with water, in the step of synthesizing the layered silicon compound including the upper reaction, the layered silicon compound is hardly manufactured as containing only Si ₆ H ₆ , and the layered The silicon compound is represented by Si ₆ H _s (OH) _t X _u (X is an element or group derived from an acid anion, s + t + u = 6, 0 <s <6, 0 <t <6, 0 <u <6). Manufactured as a product. In the above chemical formula, inevitable impurities such as Ca that can remain are not taken into consideration. A silicon material obtained by heating the layered silicon compound also contains an element derived from an anion of oxygen or acid.

As described above, the silicon material has a structure in which a plurality of plate-like silicon bodies are laminated in the thickness direction. In order to efficiently store and release charge carriers such as lithium ions, the plate-like silicon body preferably has a thickness in the range of 10 nm to 100 nm, more preferably in the range of 20 nm to 50 nm. The length in the longitudinal direction of the plate-like silicon body is preferably within a range of 0.1 μm to 50 μm. The plate-like silicon body preferably has (length in the longitudinal direction) / (thickness) in the range of 2 to 1000. The laminated structure of the plate-like silicon body can be confirmed by observation with a scanning electron microscope or the like. This laminated structure is considered to be a remnant of the Si layer in the raw material CaSi ₂ .

  The silicon material preferably includes amorphous silicon and / or silicon crystallites. In particular, the above plate-like silicon body is preferably in a state where amorphous silicon is used as a matrix and silicon crystallites are scattered in the matrix. The size of the silicon crystallite is preferably in the range of 0.5 nm to 300 nm, more preferably in the range of 1 nm to 100 nm, still more preferably in the range of 1 nm to 50 nm, and particularly preferably in the range of 1 nm to 10 nm. The size of the silicon crystallite is calculated from the Scherrer equation using X-ray diffraction measurement on the silicon material and using the half-value width of the diffraction peak of the Si (111) plane of the obtained X-ray diffraction chart. .

  The abundance and size of the plate-like silicon body, amorphous silicon and silicon crystallite contained in the silicon material mainly depend on the heating temperature and the heating time. The heating temperature is preferably in the range of 350 ° C to 950 ° C, more preferably in the range of 400 ° C to 900 ° C.

  The silicon material may be coated with carbon. A silicon material coated with carbon is excellent in conductivity.

  The average particle size of the silicon material is preferably in the range of 2 to 7 μm, and more preferably in the range of 2.5 to 6.5 μm. If a silicon material having an average particle size that is too small is used, it may be difficult to manufacture the negative electrode from the viewpoint of cohesion and wettability. Specifically, in the slurry prepared at the time of manufacturing the negative electrode, a silicon material having an average particle size that is too small may aggregate. On the other hand, a lithium ion secondary battery including a negative electrode using a silicon material having an excessively large average particle size may not be able to be charged / discharged appropriately. In the case of a silicon material having an average particle size that is too large, it is presumed that lithium ions cannot sufficiently diffuse into the silicon material. In addition, the average particle diameter in this specification means D50 when a sample is measured with a general laser diffraction type particle size distribution measuring apparatus.

  Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, and carboxymethylcellulose. What is necessary is just to employ | adopt well-known things, such as a styrene butadiene rubber.

  A cross-linked polymer obtained by cross-linking a carboxyl group-containing polymer such as polyacrylic acid or polymethacrylic acid with a polyamine such as diamine disclosed in International Publication No. 2016/063882 may be used as a binder.

  Examples of the diamine used in the crosslinked polymer include alkylene diamines such as ethylene diamine, propylene diamine, and hexamethylene diamine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, isophorone diamine, and bis (4-aminocyclohexyl) methane. Saturated carbocyclic diamine, m-phenylenediamine, p-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, bis (4-aminophenyl) sulfone, benzidine, o-tolidine, 2,4- Aromatic diamines such as tolylenediamine, 2,6-tolylenediamine, xylylenediamine, and naphthalenediamine are exemplified.

  The blending ratio of the binder in the active material layer is preferably a mass ratio of active material: binder = 1: 0.005 to 1: 0.3. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

  The conductive assistant is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be added arbitrarily when the electrode conductivity is insufficient, and may not be added when the electrode conductivity is sufficiently excellent. The conductive auxiliary agent may be any chemically inert electronic high conductor, and examples thereof include carbon black, graphite, Vapor Grown Carbon Fiber, and various metal particles. The Examples of carbon black include acetylene black, ketjen black (registered trademark), furnace black, and channel black. These conductive assistants can be added to the active material layer alone or in combination of two or more. The blending ratio of the conductive assistant in the active material layer is preferably a mass ratio of active material: conductive assistant = 1: 0.01 to 1: 0.5. This is because if the amount of the conductive auxiliary is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary is too large, the moldability of the active material layer is deteriorated and the energy density of the electrode is lowered.

  In order to form an active material layer on the surface of the current collector, a current collecting method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method can be used. An active material may be applied to the surface of the body. Specifically, an active material, a binder, a solvent, and a conductive additive as necessary are mixed to form a slurry, and the slurry is applied to the surface of the current collector and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried product may be compressed.

  The ion conductive material layer formed on the surface of the active material layer will be described. Since the ion conductive material layer is formed on the surface of the active material layer, direct contact between the electrolytic solution and the active material can be suppressed, so that deterioration of the positive electrode active material, the negative electrode active material, or the electrolytic solution can be prevented. . In the case of the positive electrode in which the ion conductive material layer is formed on the surface of the positive electrode active material layer, the oxidative decomposition of the electrolytic solution can be mainly suppressed, and the ion conductive material layer is the surface of the negative electrode active material layer. In the case of the negative electrode formed in the above, reductive decomposition of the electrolytic solution can be mainly suppressed. In particular, the positive electrode of the present invention in which the positive electrode active material layer is coated with an ion conductive material layer can be used under a high potential condition of 4.3 V or higher, 4.5 V or higher, or 4.7 V or higher. .

  The thickness of the ion conductive material layer is not particularly limited, but is preferably 0.01 to 20 μm, more preferably 0.05 to 15 μm, further preferably 0.1 to 10 μm, and particularly preferably 0.5 to 5 μm.

  In order to provide the ion conductive material layer on the surface of the active material layer, for example, the reaction liquid after the reaction step of the production method of the ion conductive material of the present invention is appropriately adjusted to an appropriate concentration, and the active material layer What is necessary is just to implement a drying process, after implementing the application | coating process apply | coated to the surface. In the coating process, a conventionally known method such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method may be used. The drying step may be performed under normal pressure conditions or under reduced pressure conditions using a vacuum dryer. What is necessary is just to set drying temperature suitably in the range which an ion conductive material does not decompose | disassemble, and the temperature beyond the boiling point of a reaction solvent is preferable. What is necessary is just to set drying time suitably according to an application quantity and drying temperature.

  The secondary battery of the present invention includes the electrode of the present invention. In the secondary battery of the present invention, both the positive electrode and the negative electrode may be the electrode of the present invention, or one of the electrodes is the electrode of the present invention, and the other does not have an ion conductive material layer. May be a typical electrode.

  Specific configurations other than the electrodes in the lithium ion secondary battery of the present invention include a separator and an electrolytic solution.

  The separator separates the positive electrode and the negative electrode and allows lithium ions to pass while preventing a short circuit due to contact between the two electrodes. A known separator may be employed, such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polyamide), polyester, polyacrylonitrile or other synthetic resin, cellulose, amylose or other polysaccharide, fibroin. And porous materials, nonwoven fabrics, woven fabrics, and the like using one or more electrical insulating materials such as natural polymers such as keratin, lignin, and suberin, and ceramics. The separator may have a multilayer structure.

  The electrolytic solution includes a nonaqueous solvent and an electrolyte dissolved in the nonaqueous solvent.

  As the non-aqueous solvent, cyclic esters, chain esters, ethers and the like can be used. Examples of cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone. Examples of chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, ethyl methyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. As the non-aqueous solvent, a compound in which part or all of hydrogen in the chemical structure of the specific solvent is substituted with fluorine may be employed.

Examples of the electrolyte include lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , and LiN (CF ₃ SO ₂ ) ₂ .

As an electrolytic solution, 0.5 mol / liter of a lithium salt such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO _{3 is} added to a non-aqueous solvent such as fluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. A solution dissolved at a concentration of about 1.7 mol / L from L can be exemplified.

A specific method for producing the lithium ion secondary battery of the present invention will be described.
For example, a separator is sandwiched between a positive electrode and a negative electrode to form an electrode body. The electrode body may be any of a stacked type in which a positive electrode, a separator and a negative electrode are stacked, or a wound type in which a positive electrode, a separator and a negative electrode are stacked. After connecting the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal connected to the outside using a current collecting lead or the like, an electrolyte is added to the electrode body to form a lithium ion secondary battery. Good.

  The shape of the lithium ion secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, and a laminate shape can be adopted.

  The lithium ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy generated by a lithium ion secondary battery for all or a part of its power source. For example, the vehicle may be an electric vehicle or a hybrid vehicle. When a lithium ion secondary battery is mounted on a vehicle, a plurality of lithium ion secondary batteries may be connected in series to form an assembled battery. Examples of devices equipped with lithium ion secondary batteries include various home appliances driven by batteries such as personal computers and portable communication devices, office devices, and industrial devices in addition to vehicles. Furthermore, the lithium ion secondary battery of the present invention includes wind power generation, solar power generation, hydroelectric power generation and other power system power storage devices and power smoothing devices, power supplies for ships and / or auxiliary power supply sources, aircraft, Power supply for spacecraft and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as a power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, You may use for the electrical storage apparatus which stores temporarily the electric power required for charge in the charging station for electric vehicles.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited by these Examples.

Example 1
A polyacrylic acid solution was prepared by dissolving 0.5 parts by mass of polyacrylic acid (weight average molecular weight 250,000, Wako Pure Chemical Industries, Ltd.) in 4.5 parts by mass of ethanol. In addition, a diphosphorus pentoxide solution was prepared by dissolving 0.985 parts by mass of diphosphorus pentoxide in 2 parts by mass of ethanol. The diphosphorus pentoxide solution was dropped into the polyacrylic acid solution and then stirred for 2 hours to prepare the solution of Example 1. Ethanol having a water content of 100 ppm or less was used.
In the solution of Example 1, the ratio of the number of moles of acrylic acid monomer constituting polyacrylic acid to the number of moles of diphosphorus pentoxide is 1: 1. In other words, the value of (number of moles of carboxylic acid groups in the carboxylic acid group-containing polymer to be used) / (number of moles of phosphorus in the pentavalent phosphorus compound to be used) is 1/2.

  The solution of Example 1 was applied to the surface of an aluminum foil in a film form, and then heated to remove ethanol, thereby producing the film-form ion conductive material of Example 1.

(Example 2)
To 3 g of the solution of Example 1, 15 mg of calcium hydroxide powder as a Group 2 element compound was added and stirred at 60 ° C. It was observed that calcium hydroxide was gradually dissolved in the solution. The solution in which calcium hydroxide was dissolved was used as the solution of Example 2. In addition, since calcium hydroxide is not normally dissolved in ethanol, it is considered that the observation state described above reflects the result of the reaction of calcium hydroxide.

  The solution of Example 2 was applied to the surface of the aluminum foil in a film form, and then heated to remove ethanol, whereby the film-form ion conductive material of Example 2 was produced.

(Comparative Example 1)
A polyacrylic acid solution was prepared by dissolving 0.5 parts by mass of polyacrylic acid (weight average molecular weight 250,000, Wako Pure Chemical Industries, Ltd.) in 4.5 parts by mass of ethanol. A polyacrylic acid solution was applied to the surface of the aluminum foil in a film shape, and then heated to remove ethanol, whereby a film-form ion conductive material of Comparative Example 1 was produced.

(Evaluation Example 1: Ionic conductivity)
About the ion conductive material of Example 1, Example 2, and the comparative example 1, the ion conductivity was measured using the complex alternating current impedance measuring apparatus. The results are shown in Table 1. From Table 1, it can be seen that the ion conductive materials of Example 1 and Example 2 exhibited significantly superior ion conductivity as compared with the ion conductive material of Comparative Example 1.

(Evaluation Example 2: Infrared absorption spectrum)
Infrared absorption spectra of the ion conductive materials of Example 1, Example 2, and Comparative Example 1 were measured using an infrared spectrophotometer. The infrared absorption spectrum of Example 1 is shown in FIG. 1, the infrared absorption spectrum of Example 2 is shown in FIG. 2, and the infrared absorption spectrum of Comparative Example 1 is shown in FIG. The horizontal axis of FIGS. 1-3 is a wave number (cm ^<-1> ), and a vertical axis | shaft is intensity | strength.

Comparing the infrared absorption spectrum of FIG. 1 with the infrared absorption spectrum of FIG. 3, it can be seen that the peak shape derived from CO—O observed at 1500 to 1800 cm ⁻¹ changes greatly. Further, in the infrared absorption spectrum of FIG. 1, a peak derived from P═O bond was observed at 1700 to 1750 cm ⁻¹ and a peak derived from P—O bond was observed at 1000 to 1020 cm ⁻¹ . A broad peak around 3300 cm ⁻¹ derived from the OH bond observed in the infrared absorption spectrum of FIG. 3 was hardly observed.
From these results, it can be said that the ion conductive material of Example 1 contains a —CO—O—PO structure formed by a reaction between a carboxylic acid group and P ₂ O ₅ . Further, the infrared absorption spectrum of FIG. 1, C-H peak derived from a coupling point that observed 2900～3000Cm ^-1, and, O-H bonds derived to 3300 cm ^-1 vicinity hardly observed a peak of Considering the points that have not been made, it can be said that the ion conductive material of Example 1 contains a —CO—O—PO (OEt) ₂ structure.

Further, when comparing the infrared absorption spectrum of FIG. 1 with the infrared absorption spectrum of FIG. 2, a peak derived from a Ca—O bond was clearly observed in the vicinity of 980 cm ^{−1 in} the direction of FIG. 2. Considering this result together with the fact that almost no peak near 3300 cm ⁻¹ derived from the O—H bond was observed in the infrared absorption spectrum of FIG. 2 and that the Ca ion was divalent, The ion-conductive material of Example 2 was produced by reacting Ca (OH) ₂ with the -CO-O-PO (OEt) ₂ structure, -COO-PO (OEt) -O-Ca-O-PO. It can be said to contain (OEt) -OCO-structure.

Example 1-P
Using the solution of Example 1, the positive electrode and lithium ion secondary battery of Example 1-P were produced as follows.

1.8 parts by mass of spinel-structured LiMn _1.5 Ni _0.5 O ₄ as a positive electrode active material, 0.1 parts by mass of acetylene black as a conductive additive, and 8% by mass of polyvinylidene fluoride as a binder The slurry containing N-methyl-2-pyrrolidone solution containing 1.25 parts by mass and an appropriate amount of N-methyl-2-pyrrolidone was prepared. An aluminum foil having a thickness of 15 μm was prepared as a positive electrode current collector. The slurry was applied in a film form on the surface of the aluminum foil. The aluminum foil coated with the slurry was dried to remove N-methyl-2-pyrrolidone. Then, the said aluminum foil was pressed and the 35-micrometer-thick positive electrode precursor which consists of aluminum foil in which the positive electrode active material layer was formed was manufactured.

  The solution of Example 1 was applied to the surface of the positive electrode precursor in the form of a film, and then heated to remove ethanol, thereby providing a positive electrode active material layer coated with an ion conductive material layer having a thickness of several μm. A positive electrode of Example 1-P was manufactured.

The positive electrode of Example 1-P was cut into a diameter of 15 mm to obtain an evaluation electrode. A metal lithium foil having a thickness of 500 μm was cut into a diameter of 16 mm to obtain a counter electrode. As a separator, a glass filter (Hoechst Celanese) and celgard 2400 (Polypore Corporation), which is a single-layer polypropylene, were prepared. It was also prepared an electrolyte solution obtained by dissolving LiPF ₆ at 1 mol / L in a solvent obtained by mixing 50 parts by volume of ethylene carbonate and diethyl carbonate 50 parts by volume. Two kinds of separators were sandwiched between the counter electrode and the evaluation electrode in the order of the counter electrode, the glass filter, celgard 2400, and the evaluation electrode, thereby forming an electrode body. This electrode body was accommodated in a coin-type battery case CR2032 (Hosen Co., Ltd.), and an electrolyte was further injected to obtain a coin-type battery. This was designated as the lithium ion secondary battery of Example 1-P.

(Comparative Example 1-P)
A polyacrylic acid solution was prepared by dissolving 0.5 parts by mass of polyacrylic acid (weight average molecular weight 250,000, Wako Pure Chemical Industries, Ltd.) in 4.5 parts by mass of ethanol. A positive electrode and a lithium ion secondary battery of Comparative Example 1-P were produced in the same manner as in Example 1-P except that the polyacrylic acid solution was used in place of the solution of Example 1.

(Comparative Example 2-P)
A diphosphorus pentoxide solution prepared by dissolving 0.985 parts by mass of diphosphorus pentoxide in 2 parts by mass of ethanol was prepared. A positive electrode and a lithium ion secondary battery of Comparative Example 2-P were produced in the same manner as in Example 1-P except that the diphosphorus pentoxide solution was used in place of the solution of Example 1.

(Comparative Example 3-P)
Except for using the positive electrode precursor of Example 1-P as the positive electrode of Comparative Example 3-P without using the solution of Example 1, the same method as in Example 1-P was used. A lithium ion secondary battery was manufactured.

(Evaluation Example 3: Capacity maintenance rate of positive electrode coated battery)
The lithium ion secondary batteries of Example 1-P and Comparative Example 1-P to Comparative Example 3-P were charged to 4.9 V at a constant current of 0.3 C rate, and then constant current of 0.3 C rate The charge / discharge cycle of discharging to 3.5 V was repeated 20 times. The capacity retention rate was calculated according to the following formula. The results are shown in Table 2.
Capacity maintenance rate (%) = 100 × (discharge capacity at 20th cycle) / (discharge capacity at 1st cycle)

  From the results in Table 2, it can be said that the coating effect of the ion conductive material of the present invention was supported. Since the positive electrode of Example 1-P is coated with the ion conductive material of the present invention, direct contact between the positive electrode active material and the electrolytic solution is suppressed, and oxidative decomposition of the electrolytic solution is suppressed. The lithium ion secondary battery of Example 1-P is considered to have an excellent capacity retention rate. Normally, it is considered that the electrolytic solution is oxidatively decomposed by contacting with the positive electrode active material in an oxidized state under the charging condition of 4.9V.

  Further, in view of the results of Comparative Example 1-P and Comparative Example 2-P and the result of Comparative Example 3-P, in the chemical structure of only polyacrylic acid or diphosphorus pentoxide, the positive electrode active material or the electrolytic solution It can be said that some deterioration is caused or the deterioration of the positive electrode active material or the electrolytic solution cannot be suppressed.

  In the ion conductive material of the present invention, since the -CO-O-PO structure different from the chemical structure of polyacrylic acid alone or diphosphorus pentoxide alone is formed, the positive electrode active material or the electrolytic solution is deteriorated. It is considered that the deterioration of the positive electrode active material or the electrolyte solution was remarkably suppressed and the function as an excellent protective layer was exhibited.

Example 1-N
Using the solution of Example 1, the negative electrode and lithium ion secondary battery of Example 1-N were produced as follows.

CaSi ₂ was added to a concentrated hydrochloric acid solution at 0 ° C. under stirring conditions and reacted for 1 hour. Water was added to the reaction solution, filtration was performed, and a yellow powder was collected by filtration. The yellow powder was washed with water, further washed with ethanol, and then dried under reduced pressure to obtain a layered silicon compound containing layered polysilane. Next, the layered silicon compound was heated at 800 ° C. in an argon atmosphere to release hydrogen to produce a silicon material. A carbon-coated silicon material was manufactured by heating the silicon material at 880 ° C. in a propane gas atmosphere.

  Polyacrylic acid (weight average molecular weight 250,000, Wako Pure Chemical Industries, Ltd.) was dissolved in N-methyl-2-pyrrolidone to produce a polyacrylic acid solution containing 15% by mass of polyacrylic acid. Further, 4,4′-diaminodiphenylmethane (Tokyo Chemical Industry Co., Ltd.) is dissolved in N-methyl-2-pyrrolidone, and 4,4′-diaminomethane containing 50% by mass of 4,4′-diaminodiphenylmethane is contained. A diphenylmethane solution was prepared. Under a nitrogen atmosphere, a mixture of 12.7 parts by mass of the polyacrylic acid solution and 1.05 parts by mass of the 4,4′-diaminodiphenylmethane solution was stirred at room temperature for 30 minutes, and further stirred at 110 ° C. for 2 hours. A binder solution was produced.

  72.5 parts by mass of a carbon-coated silicon material as a negative electrode active material, 13.5 parts by mass of acetylene black as a conductive additive, and the above binder solution in an amount of 14 parts by mass as a binder, and an appropriate amount N-methyl-2-pyrrolidone was mixed to produce a slurry. A copper foil having a thickness of 30 μm was prepared as a negative electrode current collector. The slurry was applied in a film form on the surface of the copper foil using a doctor blade. The copper foil coated with the slurry was dried to remove N-methyl-2-pyrrolidone. Thereafter, the copper foil was pressed to obtain a bonded product. The obtained joined product was heat-dried at 180 ° C. for 2 hours with a vacuum dryer to produce a negative electrode precursor on which a negative active material layer having a thickness of 20 μm was formed. The mixture of polyacrylic acid and 4,4′-diaminodiphenylmethane used as the binder was subjected to a dehydration reaction by the above-mentioned heat drying, and the polyacrylic acid was crosslinked with 4,4′-diaminodiphenylmethane. Change to cross-linked polymer.

  The solution of Example 1 was applied to the surface of the negative electrode precursor in the form of a film, and then heated to remove ethanol, thereby providing a negative electrode active material layer coated with an ion conductive material layer having a thickness of several μm. A negative electrode of Example 1-N was manufactured.

The negative electrode of Example 1-N was cut into a diameter of 11 mm to obtain an evaluation electrode. A metal lithium foil having a thickness of 500 μm was cut into a diameter of 16 mm to obtain a counter electrode. As a separator, a glass filter (Hoechst Celanese) and celgard 2400 (Polypore Corporation), which is a single-layer polypropylene, were prepared. It was also prepared an electrolyte solution obtained by dissolving LiPF ₆ at 1 mol / L in a solvent obtained by mixing 50 parts by volume of ethylene carbonate and diethyl carbonate 50 parts by volume. Two kinds of separators were sandwiched between the counter electrode and the evaluation electrode in the order of the counter electrode, the glass filter, celgard 2400, and the evaluation electrode, thereby forming an electrode body. This electrode body was accommodated in a coin-type battery case CR2032 (Hosen Co., Ltd.), and an electrolyte was further injected to obtain a coin-type battery. This was designated as the lithium ion secondary battery of Example 1-N.

(Example 2-N)
A negative electrode and a lithium ion secondary battery of Example 2-N were produced in the same manner as in Example 1-N, except that the solution of Example 2 was used instead of the solution of Example 1.

(Example 3-N)
To 3 g of the solution of Example 1, 20 mg of sodium hydroxide powder was added and stirred at 60 ° C. It was observed that sodium hydroxide was gradually dissolved in the solution. The above solution in which sodium hydroxide was dissolved was used as the solution of Example 3.
A negative electrode and a lithium ion secondary battery of Example 3-N were produced in the same manner as in Example 1-N, except that the solution of Example 3 was used.

(Comparative Example 1-N)
A polyacrylic acid solution was prepared by dissolving 0.5 parts by mass of polyacrylic acid (weight average molecular weight 250,000, Wako Pure Chemical Industries, Ltd.) in 4.5 parts by mass of ethanol. A negative electrode and a lithium ion secondary battery of Comparative Example 1-N were produced in the same manner as in Example 1-N, except that the polyacrylic acid solution was used instead of the solution of Example 1.

(Comparative Example 2-N)
A diphosphorus pentoxide solution prepared by dissolving 0.985 parts by mass of diphosphorus pentoxide in 2 parts by mass of ethanol was prepared. A negative electrode and a lithium ion secondary battery of Comparative Example 2-N were produced in the same manner as in Example 1-N, except that the diphosphorus pentoxide solution was used instead of the solution in Example 1.

(Comparative Example 3-N)
Comparative Example 3-N was prepared in the same manner as Example 1-N, except that the negative electrode precursor of Example 1-N was used as the negative electrode of Comparative Example 3-N without using the solution of Example 1. A lithium ion secondary battery was manufactured.

(Evaluation Example 4: Capacity maintenance rate of negative electrode coated battery)
The lithium ion secondary batteries of Example 1-N to Example 3-N and Comparative Example 1-N to Comparative Example 3-N were charged to 0.01 V at a constant current of 0.3 C rate, and then 0 The charge / discharge cycle of discharging to 1.0 V at a constant current of 3C rate was repeated 20 times. The capacity retention rate was calculated according to the following formula. The results are shown in Table 3.
Capacity maintenance rate (%) = 100 × (discharge capacity at 20th cycle) / (discharge capacity at 1st cycle)

From the results in Table 3, it can be said that the coating effect of the ion conductive materials of Example 1-N and Example 2-N was supported. In particular, it can be said that the capacity maintenance rate of the lithium ion secondary battery of Example 2-N is remarkably high.
A silicon material that is a negative electrode active material undergoes large expansion and contraction during charge and discharge. In the negative electrode of Example 2-N, Ca cross-linked the —CO—O—PO structure-containing polymer to form a tough and flexible protective layer, and the protective layer follows the expansion and contraction of the silicon material. It was thought that this was reflected in the above results.

Further, when the negative electrode of Example 3-N was immersed in the electrolytic solution, it was observed that the ion conductive material layer was dissolved in the electrolytic solution. It is considered that due to the presence of Na, the solubility of the ion conductive material layer in the electrolytic solution is increased. In Table 3, it can be said that the capacity retention rate of the lithium ion secondary battery of Example 3-N was low because the ion conductive material layer was dissolved in the electrolyte solution and could not function as the negative electrode protective layer. . From this result, it can be said that the -CO-O-PO (ONa) ₂ structure-containing polymer is unsuitable for use as a protective layer of at least a non-aqueous secondary battery.

Claims (6)

  An ion conductive material comprising a CO—O—PO structure-containing polymer. The ion conductive material according to claim 1, comprising a —CO—O—PO (OR) ₂ structure-containing polymer, wherein each R is independently selected from hydrogen, an alkyl group, or a Group 2 element.   A power storage device comprising the ion conductive material according to claim 1.   A power storage device comprising an electrode coated with the ion conductive material according to claim 2.   The manufacturing method of the ion conductive material of Claim 1 or 2 including the reaction process of a carboxylic acid group containing polymer or its salt, and a pentavalent phosphorus compound.   A method for manufacturing a power storage device, comprising a step of covering an electrode with the ion conductive material according to claim 2.